Performance optimisation of two-stage exoreversible thermoelectric heat pump in electrically series, parallel and isolated configurations

A configuration of the behaviour of an exoreversible two-stage semiconductor thermoelectric heat pump (TEHP) in three different modes, i.e., electrically series, electrically parallel and electrically separated is devised. The TEHP performance assuming Newton's heat transfer law is evaluated through a combination of finite time thermodynamics (FTT) and non-equilibrium thermodynamics. A formulation based on the heating load versus working electrical current and coefficient of performance (COP) versus working electrical current is applied in this study. For fixed total number of thermoelectric elements, optimisation of number of thermoelectric elements of the top stage for maximising the heating load and COP is done here. The complete analysis of effects of various design parameters on the performance of TEHP is formulated. Three thermodynamic models for multi-stage TEHP system considering internal irreversibilities are developed in the matrix laboratory Simulink environment. For typical operating conditions of TEHP system with total 30 thermocouples, the maximum value of COP is improved from 4.56 to 5.20 for same current in electrically parallel mode. This analysis will be helpful in designing the actual multistage TEHPs.